Optics alignment and calibration system

ABSTRACT

A multi-use assay system accurately docks a removable test strip supporting a reagent-analyte reaction with an optics system including an LED, photodetector, and lenses or light pipes for directing light to and from the test strip. Docking is achieved using alignment fixturing, whereby an optics block holder is relied upon to align the test strip and test pad with the various optical components. Signals from the photodetector indicative of test strip reaction progress are provided to a processor for measuring the analyte.

FIELD OF THE INVENTION

The present invention relates to a method and device for thedetermination of an analyte in a body fluid sample and providing a meansof reliably incorporating calibration information when each test isconducted.

BACKGROUND OF THE INVENTION

Many qualitative and quantitative diagnostic self-tests have developedin the clinical field utilizing bodily fluids from humans or animals asa sample. Many such devices have been developed for the analysis ofblood glucose in humans. However, additional analytes may be found andthe concentration determined if the appropriate low cost system wasavailable.

One common means for the determination of an analyte in a body fluidsample is through the use of reflectance measurements using aspectrophotometer and test strip or by alternatively using a biosensorsystem. The biosensor system has been popular in more recent timesbecause of the ability for a biosensor to use small sample sizes 3 to 5μls where as traditional reflectance systems usually requiresubstantially more sample in the range of 5 to 10 μls. However, thebiosensor systems tend to be affected by numerous interference's foundin the body fluid samples whereas, the reflectance measurements tend tobe less affected and therefore provide more accurate results.

The need for a low cost system which permits low volume sample sizeutilization and accurate results is important to the diagnostic fieldand could make the monitoring of chronic disease applications moreachievable.

The National Institute of health conducted a large scale study toevaluate the benefit of long term tight control of blood glucosemonitoring. The study known as the DCCT proved that long term tightcontrol of the blood glucose levels in patients with diabetes had adirect relationship to the health of the patient. One way for themedical profession to monitor the control of their patients is throughthe use of low cost, convenient monitors with memory.

Many diabetics currently use a test method described in U.S. Pat. No.5,304,468 to Phillips et al. This system is comprised of an electronicmeter and disposable dry reagent test strip. The meter reads the colorchange of the test strip after the blood sample has been applied andconverts this to an approximate reading of the concentration of glucosein the blood sample. The test strips have some variation to them and thepatient must select the appropriate calibration level prior to using thetest strip to monitor their blood. In this way the meter can accommodatevarious strip performance issues. The system also uses a complex dualoptics system to resolve the reflectance reading.

U.S. Pat. No. 4,637,403 to Garcia et al. Describes an integrated systemwhich provides a method by which the patient lances the finger to get asample of blood which is then used by the device to provide a reading ofthe blood glucose or other analyte concentration. This system uses acomplex reflectance system to read the analyte level in the sample.

U.S. Pat. No. 5,279,294 to Anderson et al. Describes a hand held shirtpocket device for the quantitative measurement of glucose in a bloodsample. The device uses sophisticated optics and test strip system toachieve a reading.

U.S. Pat. No. 5,515,170 to Matzinger et al. Describes at thedifficulties of keeping a reagent test strip aligned with an opticssystem.

European Patent Specification 0 351 891 B1 Hill et al. Describes anelectrochemical sensor system and electrodes which are suitable formeasuring the concentration of an analyte in a body fluid sample. Thesystem requires the use of expensive electrodes and reader to determinethe analyte concentration level.

U.S. Pat. No. 4,994,167 to Shults et al. Describes a measuring devicefor determining the presence and amount of a substance in a biologicalfluid using electrochemical means.

U.S. Pat. No. 5,580,794 to Allen et al. Describes a single usedisposable-measuring device for determining the presence and amount of asubstance in a biological sample using reflectance methods. The systemuses optics and electronics which are mated on a single plane.

U.S. Pat. No. 5,522,255 to Neel et al. Describes a fluid dose, flow andcoagulation device which uses a non-volatile electronic calibrationdevice to check the calibration of the reagent strip.

U.S. Pat. No. 5,053,199 to Keiser et al. describes a biosensing meterwith a pluggable memory key. This device uses a plugable memory key tocontrol the operations of the meter.

The above patent disclosures are incorporated herein by reference intheir entirety.

Although many improvements have been made, the cost and complexityneeded to read the analyte concentration of a body fluid is stillsignificant. The need to match calibration of a meter to the strips andthe system of holding a test strip in alignment with the optics has beenproblematic and led to numerous errors in analyte concentrationreadings.

Currently, existing calibration mechanisms require the loading of acalibration chip, strip or manually inputting a calibration code intothe meter. These devices can be reused numerous times resulting inerrors by the patient who do not chance or enter the appropriatecalibration data.

In addition, a system which requires a smaller body fluid sample wouldmake it more convenient for the patient and coupled with the improvedaccuracy found in reflectance devices compared to electro chemical wouldmake the monitoring simpler and more accurate.

An additional issue is the use of test strips which are out of date. Oldtest strips which are expired can lead to errors and inaccurate results.By providing a means to eliminate the use of expired test strips thepatients will not have to monitor the expiration date of the test stripsand eliminates patient errors from using old test strips.

SUMMARY OF THE INVENTION

The invention overcomes the deficiencies found in current devicesdescribed in the prior art by providing a system which is specificallydesigned to focus the optical signal from the emitting source and backto the detecting device after being reflected off of a test strip whichchanges color based on a scalable chemical reaction. The instrument canuse either focused lenses or light piping to direct the light from theemitter to the test strip reflectance surface and focus the reflectedlight back to the detection system. By doing this, the system permitsthe use of small amounts of test strip carrier to be used which reducethe amount of sample absorbed in the test strip carrier. The key toaccomplishing this is to provide the means to focus the light on a smallsite and refocus the reflected light so that it is channeled to theappropriate detector. The means of focusing also permits the use of lowcost optical components such as LED's and photodetectors formed from rawdie elements and are placed by automated placement equipment withrespect to predetermined targets on the printed circuit board.

The system must also be able to accurately dock the test strip with theoptics system including led, detector, lenses or light pipes. To achievethis a centerline alignment, or fixturing system which minimizesrotation of the test strip carrier is required. The need to accuratelydescribe the test strip performance with respect to the analyteconcentration also helps accuracy.

An advantageous feature of this system is the use of small sample sizesto test for analyte concentrations. This provides a convenience to thepatient not found in the prior art as to the amount of sample requiredfor these devices is in excess of 5 μls.

Another advantage is the minimization of strip to meter calibrationerrors by using a read writeable calibration system which prevents reuseafter the test strip supply is used up, prevents inadvertent use of teststrips which are older than the expiration date of the package.

Another advantage is the alignment of the test strip with the metertesting system to provide a means of reducing the error which is need tocompensate for poor strip to optics alignment.

This invention provides a multi-use digital electronic instrument thatis entirely self-contained. The device consist of a low cost opticssystem and the optics/lightpiping to provide adequate concentration ofemitted and reflected light to perform a reflectance test. The system ofthis invention is useful in connection with the synchronized test kitand system disclosed in application Ser. No. 08/960,866 filed Oct. 30,1997, the optics system disclosed in application Ser. No. 08/990,084filed Dec. 12, 1997, and/or the test system disclosed in applicationSer. No. 09/104,749 filed Jun. 25, 1998. The disclosures of the abovepatent applications are incorporated herein by reference in theirentirety.

BRIEF DESCRIPTION OF THE DRAWINGS

Many advantages of the current invention will be apparent to one skilledin the art with a reading of this specification in conjunction with theattached drawings, wherein like references numerals are applied to likeelements and wherein:

FIG. 1 is an exploded view of the optics system

FIG. 2 is a schematic of the electronics system showing the calibrationdevice and its relationship to the measurement means.

FIG. 3 is a partial section and an elevation view of the optics system.

FIG. 4 shows the strip alignment features for aligning the strip to thestrip holder.

FIG. 5A is a block diagram showing the processing operation of theinvention.

FIG. 5B illustrates the test strip with a test pad.

DESCRIPTION OF THE INVENTION

The present invention is preferably utilized in multi-use digitalelectronic instruments and assay devices described in detail in theabove-identified patent applications and previously incorporated byreference.

FIG. 1 is an exploded view of the optics system which comprises use of astrip 1, which has a alignment dentent 5 and pin 10, and comprisesoptics shield 15 with alignment dentent pin 20 and slot 25, optics lens30 with led focusing lens 35 and reflectance focusing lens 40, opticsblock holder 45 which positions the optics block relatively to theoptics components LED 50 and photodetector 60 which are aligned to theholes 68 and 70 in the printed circuit board 75. The photodetector 60and LED 50 are affixed to the printed circuit board 75 by using adhesive125. The LED 50 and photodetector 60 formed from raw die elements andare place by automated placement equipment with respect to predeterminedtargets on the printed circuit board hole 68.

The printed circuit board is part of a reflectometer 151 which includesa printed wiring assembly having a printed circuit board (PCB) 75,microprocessor 80 and A to D conversion circuits 85.

Test strip 1 is provided with an alignment mechanism which may havefeatures 5 and 10 designed to mate with features 20 and 25 on opticsshield 15. These are designed to issue positive alignment of the teststrip to the optics. It is contemplated that other configurationsmeeting the intent of the invention are within the scope of thisinvention.

FIG. 2 is a schematic of the electronics system which is attached to theprinted circuit board 75 of FIG. 1. These components include componentsLED 50 and photodetector 60 used to illuminate and collect the reflectedlight from the test strip, microprocessor 80, A to D conversion circuits85, calibration EEPROM 90 and electrical communication traces connectingthe EEPROM to the microprocessor 80, electrical communication tracesconnecting the microprocessor and forming a serial communication port100.

The LED 50 and photodetector 60 are attached to the printed circuitboard 75 by the use of die attach and wire bonding. The die attachmachine aligns the two devices so that they are located within 0.002inches of true positioning with respect to alignment holes 68 and 70.This accurate positioning provides the alignment necessary to permit theoptics block lenses to accurately focus the light emitted from the LEDto be directed and focused on the center of the test strip accuratelycaptured in the optics block shield system.

FIG. 3 is a partial section of an elevation view of the optics system.The test strip 1 is designed to be inserted in the collated system. Themeter housing 110 has pressure tongue 120 molded into it. It is designedto provide pressure to the strip 1 so that it is sufficiently locked inplace and will not move during testing. The locking system shown in FIG.1 consisting of features 5, 10, 20 and 25 are used to lock the strip 1to the shield 15. The optics lens 30 with LED focusing lens 35 andreflectance focusing lens 40 provides the light piping system to directthe light to and from the optics components LED 50 and photodetector 60.Optics block holder 45 positions the optics block relative to the opticscomponents LED 50 and photodetector 60 which are aligned to the holes 68and 70 in the printed circuit board 75. The photodetector 60 and LED 50are affixed to the printed circuit board 75 by using adhesive. Theoptics lens system 30 comprising lens 35 and 40 could be replaced withlight piping components such as glass fiber or coated reflective hollowtube.

FIG. 4 shows the strip alignment features for aligning the strip to thestrip holder. The alignment features found in the strip 1 are detent 5and pin 10 which mate with to optics shield 15 with alignment detent pin20 and slot 25. The optics assembly consisting of optics lens 30, opticsshield 15 and optics block holder 45 is a generally planar supporthaving at least a top face 148 and a bottom face 150. The bottom face150 is configured to receive illumination from the LED 50, and theoptics lens 30 directs the illumination to one or more test areas 190 onstrip 1. The top face 148 of the optics assembly is also configured totransmit the diffusely reflected optical radiation returning from thesampling areas 190 to the detector 60.

A reference detector may also be incorporated into the invention toprovide a means of monitoring the power and the LED performance. Thisarrangement is designed to permit the system to monitor this performanceand allow for compensation as the system ages.

In another aspect of this invention, an optical arrangement inaccordance with the invention is provided with a molded plastic lenssystem 30 to focus light to and from the sample on the test pad 12. Suchan arrangement provides the capability of focusing the light to and froma small reaction area, which reduces the size of the test pad 12 andreduces the amount of sample 250 required to effect the testingprocedure. Advantages thus realized include reduction in size/cost ofthe matrix employed and quantity of expensive reagents required. Thishas the additional benefit of minimizing the sample size required to runthe test because the void volume of the matrix times the area dictatesthe volume of sample required to run the test.

The optics of the invention may include appropriate optical filtering tooptimize measurement, or electronic filtering and masking techniques maybe employed to improve signal-to-noise levels

In another aspect the optical configuration of this invention usesmultiple LED and photodetector pairs. A first pair is used to achievethe primary analyte determination. A second pair is used to monitor testinitiation and to quantify hemoglobin and hematocrit. Subsequent pairsare used to monitor native color effects of lympic and icteric samples.Additional optical pairs are used in association with added chemicalcomponents in the strip for specific determination of possibleinterference factors such as pH, specific gravity, etc. as well as forspecific determination of additional analytes such as cholesterol,triglycerides, etc. Such analysis, using different wavelengths wheredesired, provides significant benefits to overcoming interfering effectsfrom the sample and the environment. By selecting wavelength pairs whichare tuned to detect components of the test, it is possible to isolateand quantify the analyte, hematocrit and red blood cell contributions ina testing event. In accordance with the invention, interference from theenvironment is minimized by separating its effects and monitoring eachone independently using multiple optical systems. Through detection andquantification, the individual contribution to the measurement can besubtracted from the analyte measurement. With the ever decreasing costof computing power, and a unique of constructing multiple opticalsystems at very low cost, the approach of the invention is readilyapplicable to home diagnostic use.

The test strip 1 is comprised of a test pad 12 situated in a test padholder 13. This holder mounts to strip fluid delivery system 14 andparts 5 and 10 provides a means for accurately positioning the test pad12 with respect to the LED 50, and the detector 60 in addition toproviding a means for blocking ambient light from effecting theanalysis. The test pad 12 is impregnated with the appropriate chemistryto permit a colormetric analysis of the analyte being tested and maytherefore provide a stable absorbent substrate.

The test strip of this invention provides a support for the test pad.The strip positively seats on the testing instrument, assuring properalignment through center line fixturing. It also seals the optics areafrom ambient light and blood contamination. Thus, it provides all of thefunctionality of a test strip and test strip holder of a conventionalreflectance system. The test strip provides additional benefits in beingremoved after each test, facilitating easy access to the optics area forcleaning if required. With this combination part, the overall cost ofthe system is further reduced. When inserted into the detection device151, the test strip 1 contacts complete a circuit which turns the deviceon. The device is turned off upon removal of the test strip. Thiseliminates a need for a separate on/off circuit or for patient action toturn the testing instrument on or off.

The signal producing system impregnated in the test pad matrix can beformed from different indicator systems such as3-methyl-2-benzothiazolinone hydrazone (MBTH) and8-anilino-1-naphthalenessulfonate(ANS), U.S. Pat. No. 5,453,360 Yu, MBTHand 3-dimethylaminobenzoic acid (DMAB), U.S. Pat. No. 5,049,487 Phillipset al., 3-methyl-2-benzothiazolinone˜hydrazone sulfonate sodium salt(MBTH-S04) and ANS, MBTH-S04 and N-(3-sulfopropyl)aniline (HALPS),MBTH-S04 and N-Ethyl-N-(3-sulfopropyl)aniline ALPS, U.S. Pat. No.4,396,714, Maeda et. al. and U.S. Pat. No. 5,776,719 Douglas et al. Oneskilled in the art can select alternate indicator systems. The oxidaseenzyme system contained in the reagent pad produces hydrogen peroxidewhich is used to convert the indicator with the assistance of peroxidasewhich acts as the catalyst.

In a preferred embodiment the reagents are impregnated into a porousmembrane by submerging the dry membrane into a reagent dip. Excess fluidis wiped from the membrane surface and the membrane is gently dried inan oven. At this point, subsequent dipping and drying can be conducted.A preferred embodiment for a two dip process is:

MBTH-S04 & ALPS Formulation

A Dip Final Concentrations In Citrate Buffer, pH 7 0.1M stock A Dip EDTA0.08% mannitol 0.19% Gantrez-595 0.53% Kiucel 99-EF 20 μM Crotein-SPA7.45% /12 enzyme reagents Glucose Oxidase 0.92% Peroxidase 0.54% B DipIn 70% Ethanol MBTH-504 0.66% ALPS 2.00% SOS 0.20%

The assembly of a system kit comprised of a testing instrument and aspecific number of synchronized test strips for the testing of aspecific analyte can provide a simple, cost effective test method andprocedure.

FIG. 5A is a block diagram showing the processing operation of theinvention. Testing instrument 151 comprises a microprocessor 80 whichcontrols the operation of the testing instrument 151. The testinginstrument 151 is activated by a switching mechanism which may comprisea mechanical ON button 155 and contacts 160-165 which close anappropriate circuit when the button 155 is depressed. Closing of thiscircuit triggers operation of the device by notifying the microprocessor80 that a measurement reading of a positioned test strip 1 is to beperformed. The test strip may be one of a number of test strips in theset, and a counter keeps track of these. Alternatively, the circuit maybe closed via a fluid connection using the test sample, with thecontacts 170 and 175 operating as probes provided for making contactwith the test pad 12 of the test strip 1 illustrated in FIG. 5B tothereby activate the testing instrument 151 upon detection of the sampleon the appropriately positioned test strip 1.

Following activation, measurement of the reaction of the sample with thereagent on the test strip 1 is effected using the detector 60. Themicroprocessor 80 derives an electrical signal from the electro-opticaldevices the LED 50, and the detector 60, and processes it to generate adetection signal indicative of analyte concentration in the testedsample. An ASIC 185 (application-specific integrated circuit) and amemory, such as RAM (random access memory) 195 or a ROM (read onlymemory) may be used in conjunction with the microprocessor 80, while theresults of the measurement may then be displayed using LCD display 200.The results may alternatively be stored in RAM 195 for subsequentviewing or processing. The subsequent processing may be performed usingthe measuring instrument 151 itself, or using other devices to which themeasurement results can be downloaded. One possibility in accordancewith the invention is a modem link with a remote processing unit, using,e.g., telephone lines. The information may also be downloaded forstorage at an internet location or electronic bulletin board forsubsequent retrieval and processing or review by medical professionals.See application Ser. No. 09/190,301 filed Nov. 13, 1998, incorporatedherein by reference in its entirety.

One feature in accordance with the invention is the use of a calibrationchip 90 as shown in FIG. 2. The calibration chip is detachablyconnectable to the testing instrument 151 for electronic communicationwith the microprocessor 80. It may be any form of volatile ornon-volatile memory including single use microprocessors, EPROMs orEEPROMs 90. Calibration chip 90 contains calibration information whichis uniquely specific to the reagent provided with a particular set oftest strips 1 distributed with the calibration chip. In this way, lotdifferences in the reagent can be compensated for using the requiredinformation and sophistication, while at the same time obviating theneed for the user to enter or contribute to this information. Thisminimizes error and greatly facilitates use and accuracy of the testinginstrument of the invention.

The color formed after applying the bodily fluid to the reagent test padis proportional to the amount of analyte in the applied sample 250. Thetesting instrument 151, via sensor 60, ASIC 185 and microprocessor 80,measures the change in reflectance due to the development of thespecific color generated by the reagent on the test strip 1. This iseither used as the input to a function which relates reflectance toanalyte level or to a table which correlates reflectance value toanalyte level. The function or the table must be stored within thesystem for it to produce and display, on display 200, a reading of theanalyte level in the sample 250. While most meters in use today employfunctions to convert reflectance readings to analyte concentration, thisapproach requires that the function be stable and well understood. Theuse of a look up table permits the storage of specific values forreflectance and their corresponding analyte levels. The testinginstrument uses this table and interpolates between the table values togive relatively accurate readings. This is achievable in a system suchas that described by this invention as the table can quickly begenerated for each reagent lot produced.

In the preferred embodiment, calibration is based on the responseproduced by a specific lot of test strips. In this manner, there is noneed to presort and test the LED 50 , significantly reducing the cost ofthe sensor 60. The LED 50 and photodetector 60 formed from raw dieelements and are place by automated placement equipment with respect topredetermined targets on the printed circuit board. In addition, thiscalibration step during manufacture allows the device to compensate fora wide area of variables normally found in reflectance systems. Thespecific calibration data for the test strips 1 shipped with the testinginstrument can be stored in the unit's read only memory (not shown).Alternatively, a master strip can be provided for setting thecalibration information for that lot of strips and the master strip canbe distributed therewith. A counter may be provided to limit the testinginstrument 151 to performing only a specific number of tests whichcorrelates to the quantity of test strips 1 shipped with the device.Other limitations can be built-in, such as expiration date informationpertaining to the specific lot of test strips 1, with this informationbeing contained in the measuring instrument's ROM or in the calibrationchip 90 or in the master strip.

A more traditional approach to calibration may alternatively be taken. Acalibration algorithm, with several settings if necessary, could beprogrammed into the system if the testing instrument has a longerprojected life and is to be used with multiple sets of test strips.

If a microprocessor is used for the calibration chip, the chip may beprovided with its own power source for memory information retention.Similarly, when a microprocessor or EEPROM or other memory device isused, the calibration chip 90 may have its data overwritten or anindicator bit thereof be written by the microprocessor 80 following itsuse to prevent reuse. The calibration information stored in thecalibration chip 90 is thus downloaded to the microprocessor 80, and thecalibration chip is disabled, preventing re use thereof. The calibrationinformation contains the permitted number of test strip analyses to beperformed, the number corresponding to the number of test stripsprovided with the kit. The calibration chip itself can then be disposedof.

Alternatively, a counter (not shown) may be provided in the calibrationchip, the counter being decremented each time the chip is read. In thismanner, only a limited number of readings, corresponding to the numberof test strips 1 provided with the calibration chip 90, can beperformed. It is also contemplated that calibration information providesand expiration date preventing use of the calibration chip and/orassociated strips thereafter, or a duration can be measured after whichuse of the chip and/or associated strips is precluded. The duration canbe commenced from time of opening a package in which the kit isprovided, or from any other similar time, such as the time of first useof the calibration chip 90. The ordinarily skilled artisan will findnumerous variations can be effected without departure from the spiritand scope of this invention.

The patient uses the system by removing the testing instrument from thepackaging and placing it on a firm surface. The next step is to remove atest strip and insert it in the testing instrument. Inserting the teststrip activates the unit, eliminating the need for a power on/off buttonor switch. The patient then uses either a sampler from the kit or oneprocured separately to draw a sample of capillary blood. The sample isapplied to the test strip, initiating a timing sequence, and the testinginstrument displays the results after an appropriate time.Alternatively, the patient may first apply the blood sample to the teststrip, then insert the strip into the testing instrument to activate thetest cycle and read out of test results.

The subject invention provides improvements over existing technology inuse today in several ways. The preferred embodiment of the inventioneliminates the need for a patient to purchase a costly system to conductroutine testing of body fluids. It also eliminates the existingdependence on the customer to maintain the testing instrument andmonitor or compensate for reagent lot differences. The inventionprovides this easy to use format for analytes such as glucose byincorporating advanced lens based optics and low cost modem electronics.The use of lens based optics permits the system to focus on smallreaction area which reduces the size of the test pad. The resultingsmall test pad reduces the cost of the matrix employed and the quantityof expensive reagents needed to conduct an accurate assay using anoxidase and peroxidase chemistry. With a smaller test pad, a smallersample volume is adequate. The system conserves the energy used andminimizes the amount of light required by the system to determine thecolor change. The optics modules are calibrated during the manufactureof the testing instrument.

An important feature in accordance with the invention is the manufactureand calibration of the testing instrument 151 for use with a specificquantity of test strips 1 which have been matched at the factory. Thislimits the need for calibration codes, and minimizes the maintenancerequired by the patient in the form of cleaning, battery replacement andcalibration code changes. It also improves the system's ability toprovide long term accurate results because a testing instrument issynchronized with only certain test strips. Once they have been used, acomplete new kit is acquired with a testing instrument calibratedspecifically for those test strips. This eliminates much of thecompromise in system performance found in current products which have towork with strips made over a wide range of production conditions andinput states.

The above are exemplary modes of carrying out the invention and are notintended to be limiting. It will be apparent to those skilled in the artthat modifications thereto can be made without departure from the spiritand scope of the invention as set forth by the following claims.

We claim:
 1. A multi-use assay system comprising: an electronics printedcircuit board; an optics system comprising a lens, an emitter, and adetector, wherein the emitter and detector are mounted in theelectronics printed circuit board; a removable test strip for alignmentto the optics system by means of center line fixturing; a housing forcontaining the optics system and holding the removable test strip inposition relative to the optics system; a test pad having a center line;an optics block holder keyed to align the removable test strip to thecenter line of the test pad and to mount in the electronics printedcircuit board such that the optics block holder aligns to alignmentfixturing of an emitter and detector placement machine, the optics blockholder positioning the optics system to focus the light from the emitterand to the detector; a processor for processing data from the emitterand detector; and a removable single use electronic calibration systemfor providing the processor with strip specific calibration information.2. A multi-use assay system comprising: an electronics printed circuitboard; an optics system comprising a lens, an emitter, and a detector; aremovable test strip for alignment to the optics system by means ofcenter line fixturing; a housing for holding the removable test strip tothe optics system; a test pad having a center line; an optics blockholder keyed to align the removable test strip to the center line of thetest pad and to mount in the electronics printed circuit board such thatthe optics block holder aligns to alignment fixturing of an emitter anddetector placement machine, the optics block holder positioning theoptics system to focus light from the emitter and to the detector; aprocessor for processing data from the detector; and a removable singleuse electronic calibration element for providing the processor withstrip specific calibration information containing the number ofremovable test strips associated with the calibration element andcontaining reaction information of the removable test strips.
 3. Asystem of claim 1 where the electronic calibration element backs up themeter specific calibration information.
 4. A system of claim 1 whereinthe electronic calibration element is a chip, master strip or code.
 5. Acalibration system of claim 1 where the electronic calibration elementcontains the expiration date of the test strips provided with thecalibration element.